Mick visits one of Tim’s old school mates, Gavin Smith, who runs a MakerSpace called Robots & Dinosaurs in Meadowbank, Sydney, Australia. Part 1 looks at laser cutters, CNC machines and some old school stories.

[youtube https://www.youtube.com/watch?v=xg6FHfwYh6E&w=640&h=360]

Part 1: Laser cutters, CNC and other machinery

Transcript

Intro

Mick

So, some bozo decided to delete the intro that we did previously.

Tim

Yeah, that’s right.

Mick

Who was that, Tim?

Tim

That was the guy holding the camera, because I can’t do it. I’m driving.

Mick

Oh yeah, right.

Mick

So, we’re on our way to Robots and Dinosaurs.

Tim

Yup, R&D. I’ve already seen photos on Facebook and the website. I hear they’ve got some machinery, stuff that you would find really useful, but you wouldn’t use too often. So, hard to justify buying.

Tim

Also, the space, the garage, you couldn’t. Laser Cutters are pretty big I understand. For those people who say a garage is for a car, you’re mistaken. Where am I now?

Mick

Turn right, yeah. Let’s see what it looks like.

Tim

Alright, looking forward to it, mate.

Mick

Must be upstairs.

Tim

On your phone I thought it was just there that way.

Mick

If you look at Google Maps, you can actually see it’s pointing roughly here. Okay, this is looking promising I think, maybe.

Tim

Ten?

Mick

Actually it should be ten, yeah.

Tim

14. There we go.

Mick

Ten. I don’t think it’s the Australian traditional medicine society. Maybe they’ve moved. What about this 8B?

Yeah, that’s it. The plastic you can get a bit thicker. That’s quite strong.

Tim

That’s perspex?

Gavin

Yeah.

Magic mirrors

Mick

Tim and I had a discussion on the way over. What would happen if we tried to cut a mirror?

Gavin

See that glass tube at the back there?

Mick

Yeah.

Gavin

That is a CO2 laser tube. It makes an infrared beam. So, have a look at this… Electromagnetic spectrum. You’ve got blue light here. You’ve got red light here. Every piece of visible light you have ever seen and enjoyed in your entire life has been within this little range here. The CO2 laser is over here. It’s so far away from visible light that what we think of is mirrors and what we think of as transparent doesn’t quite apply, which is why you can have a see-through window on the top rather than a totally opaque box.

Gavin

The way that you cut acrylic is that it melts and then it runs away through the gap where it vaporizes, so you’re locally heating and melting. If you try and cut metal, it’s too good at heat sink, so instead of getting one really hot spot that vaporizes and cuts, the whole thing just gets slightly warm.

Gavin

These mirrors are magic metal of some sort.

Mick

Magic metal?

Gavin

The previous slice cutter we had, copper mirrors. It just polished copper.

Mick

Oh, okay. Yeah, makes sense.

Gavin

That works really well, because it’s reflecting off the service, it’s really efficient as opposed to a glass metal mirror where it’s got to go through a layer and then out again so you’re not heating the glass.

Gavin

Inside the boxes is activated charcoal plus two layers of filtration on top of that. The idea is to just capture anything that comes out of the laser cutter, so we can be nice neighbors.

Tim

Yeah, okay. I saw that coming outside, but no, but then you filtered it.

Gavin

It’s filtered, yeah. This is a commercial filter specifically for laser cutters. This behaves worse than the one we made ourselves, so this is why this thing is disconnected and in the corner. That’s pushing in and that’s pulling out.

Mick

Okay.

Gavin

There’s a third fan inside there as well.

Tim

I take it that this second fan has to be more powerful than the blower with the positive pressure.

Gavin

No, no, it’s easier to push than it is to pull because you can push as many atmospheres as you like, but you can’t pull more than one atmosphere. If you’re pushing water in a pipe up a hill, for example, you can push it as high up as you like, but you can’t such water through a straw more than ten meters because ten meters of water is one atmosphere worth of pressure. You’d end up with a perfect vacuum at the bottom, and you can’t have a negative pressure.

Tim

Acrylic, Plywood, MDF and Bamboo sheets.

Trying not to kill yourself

Gavin

Yeah. ABS is okay. It’s a bit smelly.

Tim

One of them puts off cyanide?

Gavin

PVC.

Tim

PVC, yeah okay.

Mick

Is it chlorine gas?

Gavin

Yes, it’s chlorine gas.

Tim

Chlorine gas.

Mick

Polyvinyl chloride – Chlorine gas.

Gavin

I’ll show you how to test that if you got a sec.

Tim

Oh, okay.

Gavin

This is known as the Blowtorch Test. If you’ve got a bit of plastic, and you’re not sure whether it’s laser safe, this is a quick and dirty test you can do to see whether it contains chlorine. If it doesn’t contain chlorine that doesn’t mean it will cut well, but it just means it won’t kill you in one specific way. So, it’s a good first step.

Gavin

Ordinary bit of copper here, and a bog standard blowtorch. Just heating this up to red hot just to make sure there’s no plastic left on. We’ll dab that in our test piece, and some of the plastic ends up stuck on the tip. Now what I’m gonna do is heat it back up again. If there’s chlorine present, you’ll see a green flame come up there.

Gavin

That definitely contains chlorine, so-

Tim

No laser cutting that.

Gavin

No laser cutting that.

Tim

Or burning of any kind really?

Gavin

Yes.

Tim

That controls the laser cutters?

Gavin

That’s it.

Tim

Alright.

Making boxes

Gavin

You can see these are my little Sudoku test pieces. I was playing around with tiles of different sizes before. I want to make a Sudoku where you put the tiles in places and tangibly play around with it, but I wasn’t sure how large the slot should be compared to the tile itself. After playing around, I decided about a 20 mm tile is kind of easy to grip and play with and manipulate, and have a stack of them and not take up too much space. 21 mm pole is easy to get in and out. 3 mm clearance is enough.

Gavin

Then after playing around with it, I’m actually like, “3 mm is ridiculously large.” 1 mm of clearance is perfectly fine.

Tim

You design it on a special app?

Gavin

This is Inkscape, which is open source. It’s like Adobe Illustrator or something, but it’s open source. We output in DXF format and then take it to the machine and import it there. There’s a series of rain dance steps that we do. If you do all the steps in the rain dance, then generally your file is intact and you can cut stuff.

Mick

That’s a lot of fun.

Speaker 4

The cool thing about Inkscape though is it actually has a plugin which allows you to do boxes on the fly very quickly, square boxes with partitions, whatever.

Tim

Oh, so the software actually allows you to-

Gavin

Generates the, yeah. Say I want a box that’s this wide, this deep, this high-

Tim

It’ll make it, right?

Gavin

You can say, “My material is this thickness,” and it says, “Would you want that to be your inside or outside dimensions?” Yeah, it makes it ridiculously easy.

Mick

That is so cool.

Gavin

All you do to make the box is to just customize it and add the bits that you want. In this case, I added a nice level cutout, so I’ve got the-

Tim

It’s a cool box.

Mick

Funny you should say that, but carpentry is all about how to make a box.

Gavin

Yes.

Mick

That’s all it is.

Gavin

Totally.

Carpentry

Someone Else

That’s Gavin’s current obsession.

Gavin

Yes, this is my current obsession. This is where I got up to recently.

Mick

Nice.

Gavin

I’m happy with that.

Mick

Look at that.

Tim

What’s that? That’s a dovetail or something?

Gavin

Yeah, that’s how I got up to it.

Tim

Look how tight that is. What’s the name of this joint here?

Gavin

That’s a box joint. Because the laser cuts vertically down, which is always in a straight line, you can’t really do dove tails in the same way.

Mick

Have you seen biscuits, biscuit joints?

Getting in trouble at school

Tim

My first encounter with biscuits was with Gavin in high school where we-

Mick

Ha ha. Oh no! Is this another story is it?

Tim

Someone else had joined two bits of wood with a biscuit, and we both determined that we would snap the biscuit. We put both our weight on it and it snapped outside of the biscuit. The deputy principle came and found us, and he told everyone that two bright sparks, I still remember the phrase he used, “Two bright sparks decided to break this, and they couldn’t break the biscuit. They broke it just on the outside to show you how strong it was.”

Tim

We were embarrassed to, “See, we demonstrated something.”

Gavin

I filtered that out, but I remember that.

Tim

Yeah?

Gavin

Yeah.

CNC machines

Gavin

This is our Xcarve. This is a CNC machine. If you program in on a laptop what you want it to do, it’ll go and cut it for you. Also, the secret to having any tool in a communal environment is you need to have all the accessories and all tools there and self-enforcing, so that people know they go back in that spot. If it’s not obvious, it’ll end up everywhere and you’ll never have the machine working again.

Tim

The spot has to be obvious.

Mick

Something resting on the keyboard.

Tim

The old dust in the keyboard. Press F3 to remove dust.

Gavin

That’s it.

Tim

Do you have any samples of CNC material?

Gavin

That’s the circuit board.

Tim

Oh, good old circuit board. Of course, the middle here means you can’t laser cut it, so you’d use CNC.

Gavin

What this is doing is having a v cutter that comes down and just gouges out the groove. Technically you’re carving out the Voroni Diagram of the circuit.

Tim

So the opposite?

Gavin

The opposite, yeah. Normally you’d use three tools. You’d use v cutter to cut the actual traces out. You’d use a drill hole to put all the holes for your IC’s and internal stuff. Then you’d use a router bit to cut the edge free and make a small circuit board. It’s pretty convenient. You can do it in an hour or so, or less.

Gavin

There’s a sweet spot of like, “Do I just solder up on protoboard?” Then if it’s a little more complex, maybe I’ll make a custom circuit board on CNC. Then if it’s a little bit more complex, I’m gonna send it away to China and have it fabbed for ten dollars, but it’s gonna take me three weeks or whatever. There’s sweet spots where this machine becomes really useful.

Gavin

You can draw it in Eagle or standard CAD stuff. There’s a script for Eagle called PCB Gcode, and that will take your file and generate the motions of the cutter. To do that you can tell it how wide isolations you want and how deep.

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